This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 100 51 662.9, filed on Oct. 18, 2000, the entire disclosure of which is incorporated herein by reference.
The invention relates to a method and a system for extinguishing a fire that has broken out in an enclosed space, for example in the cabin or a freight compartment of a passenger aircraft. Nitrogen is introduced into the enclosed space so as to displace the oxygen required for maintaining the fire, thereby extinguishing the fire.
A variety of different fire extinguishing methods and systems have become known for suppressing fires in public transportation vehicles. For example, German Patent Publication 36 15 415 C2 discloses a fire extinguishing arrangement including, two containers that respectively contain fire extinguishing agents in a liquid state under pressure, for generating first and second fire extinguishing charges for freight compartments of transportation vehicles, and especially aircraft. It is also known from the German Patent Publication 39 17 205 C1, to provide a firefighting arrangement for aircraft, that includes a fire extinguishing unit equipped with a drive arrangement and adapted to be movable along the longitudinal direction of the aircraft.
It is further known in the field of aircraft technology to provide a space or cabin flooding arrangement, for example in the manner of a freight compartment fire extinguishing system, which is supplied with halon 1301 gas to flood the associated enclosed space with the halon 1301. This also applies to firefighting flooding arrangements in fuel tanks or the like. On the other hand, in ships or other maritime applications, for example in cabins and machine rooms thereof, carbon dioxide and water sprinklers or water fogging arrangements are predominantly used for fire suppression. In the construction of buildings and the like, water sprinkler systems and carbon dioxide extinguisher arrangements are predominantly used for firefighting.
Such known arrangements have several disadvantages and are not suitable for use in enclosed spaces such as the cabin and freight compartment of an aircraft or the like. For example, some of the fire extinguishing agents used in such known systems are toxic, environmentally hazardous, and may cause damage to the aircraft or goods being transported therein. Moreover, the required supply of the fire extinguishing agent adds a substantial weight to the aircraft, and in any event only provides a limited supply of the extinguishing agent which will therefore be used up or exhausted after a limited time in a fire extinguishing application.
In view of the above, it is an object of the invention to provide a method and a system of the above described general type, which can achieve a fire suppression in an enclosed space during a nearly unlimited time frame, particularly by supplying a substantially continuous or unlimited quantity of a fire extinguishing agent. It is another object of the invention to utilize a fire extinguishing agent that is nontoxic to persons or animals in the effective utilized concentrations, not hazardous to the environment, and not contributing significantly to the overall weight of the aircraft or the like. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved according to the invention in a fire extinguishing or suppression method which begins when a fire is detected in an enclosed space. Once a fire is detected, nitrogen is introduced into the enclosed space at a high rate so as to quickly increase the concentration of the inert gas nitrogen in the enclosed space in a sudden shock-like or step-like manner. Thereby, the initial rapid introduction of nitrogen into the enclosed space displaces oxygen (or generally the air) and thereby reduces the oxygen concentration in the enclosed space to a maximally effective fire extinguishing oxygen concentration. Then, in order to maintain this maximally effective fire extinguishing oxygen concentration in the enclosed space, nitrogen is further supplied at a prescribed rate or in a prescribed quantity into the enclosed space.
In other words, an initial rapid introduction of nitrogen drives the oxygen concentration down to the proper concentration for achieving a maximally effective fire suppression or extinguishing effect, and then the subsequent supply of nitrogen at a lower rate but in an essentially unlimited available supply quantity (e.g. in a continuous on-going manner for an essentially unlimited period of time) is effective to maintain the oxygen concentration at the appropriate level, preferably until the fire is extinguished. According to a particular embodiment of the invention, the maximally effective fire suppressing oxygen concentration within the enclosed space is reduced to and maintained in a range from 11 to 13 volume percent, or particularly approximately 12 volume percent, e.g. 11.5 to 12.5 volume percent.
The above objects have further been achieved according to the invention in an apparatus or system for carrying out the above described method. Such a system includes a compressed nitrogen gas bottle and/or a nitrogen gas generator connected by a pipe or conduit system to at least one extinguishing nozzle arranged within the associated enclosed space. A flow rate or quantity limiting device is arranged in the supply pipe line connecting the compressed nitrogen gas bottle and/or the nitrogen gas generator to the extinguishing nozzles. A nitrogen preparation unit is further connected to the flow rate limiting device for providing a further or continuous supply of nitrogen to maintain the maximally effective fire extinguishing oxygen concentration in the enclosed space.
According to a particular preferred embodiment of the invention, the nitrogen preparation unit comprises a membrane system, e.g. including at least one selectively permeable membrane, for selectively permeating nitrogen through this membrane and thereby separating nitrogen out of environmental air that is supplied to the nitrogen preparation unit. The nitrogen outlet of this membrane system is connected to the flow rate limiting device and/or to a pressure reservoir connected to the flow rate limiting device. The nitrogen preparation unit obtains its supply of input environmental air from the air conditioning system of a land vehicle, water vehicle or aircraft, or from an exhaust air flow that is supplied through a valve.
The invention provides and achieves at least the following advantages. The input air that is supplied to the membrane system for generating the nitrogen gas is available in essentially unlimited quantities outside of the enclosed space that is to be supplied with nitrogen, i.e. to have its oxygen concentration reduced to a maximally effective fire suppressing concentration. Since only nitrogen is used as the fire suppressing agent, the present method and system do not damage or deplete the stratospheric ozone, so that the present method and apparatus are environmentally friendly. Particularly, the present method and apparatus will not contribute to the so-called xe2x80x9cgreenhouse effectxe2x80x9d. Use of the present system and method will not cause any sort of damage to the goods being transported within the vehicle, or to the cabin interior equipment, fittings and furnishings. Moreover, the fire extinguishing agent, nitrogen, when provided in a concentration effective for fire suppression or extinguishing, is non-toxic to people and animals, so that it is not necessary to provide a prior warning interval before carrying out a fire extinguishing procedure, and it is possible to carry out fire extinguishing simultaneously while evacuating persons from the enclosed space. Since the nitrogen gas is rather stable and inert, no thermal decomposition products of the nitrogen will be formed below a temperature range of 1300 to 1500xc2x0 C.
The invention can be advantageously utilized in various enclosed spaces including passenger cabins, crew cabins, and freight and cargo compartments or holds in various types of aircraft, ships, rail vehicles, public and private buildings, fuel tanks and the like, military vehicles and other military applications, industrial installations, such as in electronics compartments, freight compartments, equipment compartments, crew compartments, sleeping quarters, conference rooms, cabins, cockpits, machine control rooms, consoles and podiums, bridges, rail locomotives and self-powered cars, passenger and crew cars, freight wagons, experiment chambers and rooms of high schools, universities, and other organizations, museums, theaters, train stations, airports, hotels, military vehicles including personnel transport carriers, rocket launching bases, ammunition storage depots, machine and turbine rooms of power stations, and the like.